Device for grinding end surfaces of billet

ABSTRACT

Billets  3  are fed to billet carrying equipment  2  through billet loading equipment  28.  With actuation of a first truing-up equipment the grinding apparatus of billets at both end faces  1 , the billet placed on a tray  23  is trued-up to the side of a first grinding equipment for working on planar portions  4 A. With actuation of the first grinding equipment for working on planar portions  4 A, working on the planar portion in one end face of the billet  3  is performed by a grinding belt  46.  The billet is carried through billet carrying equipment  2  to the position of working of a first grinding equipment for chamfering  5 A. With actuation of a second truing-up equipment, a truing-up guide is pushed to cause the billet on the tray  23  is trued-up to the side of first grinding equipment for chamfering  5 A.

TECHNICAL FIELD

The present invention relates to a grinding apparatus that grinds billets such as cut-down round steel bars at both ends thereof. More specifically, the present invention relates to a grinding apparatus of billets at both end faces thereof, in which both of working on planar portions and working of chamfering on circular edge portions are carried out successively at both ends of a plurality of billets in the carrying process of the billets in a single grinding apparatus.

BACKGROUND OF THE INVENTION

Short materials of round steel bars called billets are fabricated by cutting long steel bars with a saw blade, or by cutting with a press called shear cutting or the like. In the afterward process, the billets are subjected to deformation processing to have substantially aimed shapes by putting them into press molds in a heated state with a heating furnace or in a state of ordinary temperature without heating. Common producing processes of forged articles are such that parts are accomplished through machining process after having been subjected to such forging processes.

It affects greatly the quality of accomplished articles whether the quality of billets obtained in material forming process through each of the aforementioned cutting processes is excellent or not. Billets of inferior quality necessarily affect so as to yield to final accomplished articles as forged articles having inferior quality. Usually sites where defects occur in billets are substantially defined irrespective of their cutting process and the sites are both of planar portions and circular edge portions of both end faces. That is, burrs, rolled-up parts or the like as protrusions extending out of the edge faces are generated in the planar portions and circular edge portions in the end faces of the billets during cutting process of shear cutting.

When billets containing defects such as burrs or rolled-up parts are worked through hot pressing process or cold pressing process, obtained forged articles result in defective forged articles in which shake or exfoliation may occur. Further, when billets having burrs or rolled-up parts attached thereto are worked through hot pressing process or cold pressing process, there are cases such that these protrusions are more strongly attached to the resulting forged articles because these burrs or rolled-up parts are molten. In these cases, defective parts of cracks or the like that may induce peeling phenomena or splitting are intrinsic in the surface layer portion of the forged articles after they have undergone press working.

Patent Document 1, proposed by the present applicant, discloses an apparatus for grinding planar portions at both end faces of billets, which is developed with the purpose of improving quality of forged articles and in which billets are transported automatically and defective portions such as burrs or rolled-up parts in the end faces of billets are removed in a full automatic manner. Furthermore, Patent Document 2, also proposed by the present applicant, discloses a working apparatus for chamfering circular edge portions at both end faces of billets, which is developed with the purpose of extending life of metallic molds for forging and in which billets are transported automatically and burrs or rolled-up parts in the circular edge portions at end faces of billets are removed.

In billets obtained in material forming process, defects are generated both in planar portions and circular edge portions at both end faces of the billets. Consequently, both of working on the planar portions and chamfering on circular edge portions are necessary. Regarding this, each of working on planar portions and chamfering on circular edge portions of billets is performed with individual grinding equipment in the apparatus disclosed in Patent Document 1 or Patent Document 2. Consequently, the area for placing two sets of grinding equipment becomes large and much operation energy is necessary for operating two sets of automatic billet conveyer.

DOCUMENTS OF PRIOR ART Ptent Documents [Patent Document 1]

JP, Published Patent Application No. 2010-179404

[Patent Document 2]

JP, Published Patent Application No. 2014-210312

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The present invention has been accomplished in the aforementioned background and has a following object. It is an object of the present invention to provide a grinding apparatus of billets at both end faces in which both of working on planar portions and working of chamfering on circular edge portions are carried out simultaneously at both ends of billets and which requires less energy for operation and less space for placement.

The present invention provides the following means for solving the aforementioned problems. The grinding apparatus of billets at both end faces according to the first aspect of the present invention is characterized in that it comprises:

a machine base,

a billet carrying equipment that is provided on the machine base and carries a plurality of trays placing cut billets thereon from a feeding side to a discharging side,

a first grinding equipment for working on planar portions that is provided on the machine base and performs working on the planar potion in one end face of a billet with a first circulating endless grinding belt for working on planar portions,

a second grinding equipment for working on planar portions that is provided on the machine base and performs working on the planar potion in the other end face of the billet with a second circulating endless grinding belt for working on planar portions,

a first grinding equipment for chamfering that is provided on the machine base and performs working of chamfering on the circular edge portion in one end face of a billet with a first circulating endless grinding belt for chamfering,

a first lifting equipment that is provided on the first grinding equipment for chamfering and performs lifting movement of the first endless grinding belt so as to be attached to and detached from the billet,

a second grinding equipment for chamfering that is provided on the machine base and performs working of chamfering on the circular edge portion in the other end face of the billet with a second circulating endless grinding belt for chamfering, and

a second lifting equipment that is provided on the second grinding equipment for chamfering and performs lifting movement of the second endless grinding belt so as to be attached to and detached from the billet.

The grinding apparatus of billets at both end faces according to the second aspect of the present invention is characterized in that, in the first aspect:

the first grinding equipment for chamfering is disposed adjacent to the first grinding equipment for working on planar portions towards the discharging side,

the second grinding equipment for working on planar portions is disposed adjacent to the first grinding equipment for chamfering towards the discharging side, and

the second grinding equipment for chamfering is disposed adjacent to the second grinding equipment for working on planar portions towards the discharging side.

The grinding apparatus of billets at both end faces according to the third aspect of the present invention is characterized in that, in the first or second aspect:

the billet carrying equipment carries horizontally a plurality of trays placing cut billets thereon from the feeding side to the discharging side, and

the first endless grinding belt for working on planar portions and the second grinding belt for working on planar portions are composed so as to be inclined so that the discharging side is higher than the feeding side.

The grinding apparatus of billets at both end faces according to the fourth aspect of the present invention is characterized in that, in the first or second aspect,

the movement direction of the billet carrying equipment crosses the movement direction of the grinding faces of the first endless grinding belt for working on planar portions and the second endless grinding belt for working on planar portions with an acute angle.

The grinding apparatus of billets at both end faces according to the fifth aspect of the present invention is characterized in that, in the first or second aspect,

the billet carrying equipment has a position detecting means that detects the carrying position of the tray for causing the first lifting equipment and the second lifting equipment to make up-down movement of the first endless grinding belt for chamfering and the second endless grinding belt for chamfering to make a lifting movement respectively.

The grinding apparatus of billets at both end faces according to the sixth aspect of the present invention is characterized in that, in the first or second aspect, it further comprises:

a first truing-up equipment that is provided in the billet carrying equipment and carries the billets on the trays such that the billets are trued-up on one side of the carrying course of the billet carrying equipment, and

a second truing-up equipment that is provided in the billet carrying equipment and carries the billets on the trays such that the billets are trued-up on the other side of the carrying course of the billet carrying equipment.

Advantageous Effect of the Invention

In the grinding apparatus of billets at both end faces according to the present invention, both of a grinding equipment for working on planar portions where working on planar portions in end faces of billets is performed and a grinding equipment for chamfering where circular edge portions in end faces of billets are placed along a billet carrying equipment through which billets are carried. Consequently, a grinding apparatus of billets at both end faces that requires less energy for operation and less space for placement is provided, because both of working on planar portions in end faces of billets and working of chamfering on circular edge portions are carried out with a single grinding apparatus.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a front view showing the general composition of the grinding apparatus of billets at both end faces according to the present invention.

FIG. 2 is a plan view of FIG. 1.

FIG. 3 is a front view of a first grinding equipment for working on planar portions shown in FIG. 1.

FIG. 4 is a view of one shown in FIG. 3 viewed in the direction of the arrow P.

FIG. 5A and FIG. 5B are a view showing a tray in FIG. 1, in which FIG. 5A is a front view of the tray, and FIG. 5B is a cross-sectional view of FIG. 5A taken along the line A-A.

FIG. 6A, FIG. 6B and FIG. 6C are a view showing the truing-up equipment in FIG. 1, in which FIG. 6A is a front view of the truing-up equipment, FIG. 6B is a plan view of FIG. 6A and FIG. 6C is a cross-sectional view of FIG. 6A taken along the line B-B.

FIG. 7 is a front view of a first grinding equipment for chamfering shown in FIG. 1.

FIG. 8A and FIG. 8B are a view showing a first endless grinding belt equipment for chamfering shown in FIG. 7, in which FIG. 8A is a front view of the first endless grinding belt equipment for chamfering, and FIG. 8B is a left side view of FIG. 8A.

FIG. 9 is a cross-sectional view of FIG. 7 taken along the line C-C.

FIG. 10A and FIG. 10B are a view showing operation of grinding, in which FIG. 10A is an explanatory view showing operation of the grinding equipment for working on planar portions, and FIG. 10B is an explanatory view showing operation of the grinding equipment for chamfering.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will be explained below. FIG. 1 s a front view showing the general composition of the grinding apparatus of billets at both end faces 1 according to the present invention, and FIG. 2 is a plan view of FIG. 1. Here, a machine base 11 and a machine frame 12, as main portions of the grinding apparatus of billets at both end faces 1 are shown with two-dot chain lines. As shown in FIGS. 1 and 2, the machine base is a fixed portion placed on the floor and the machine frame 12 is a frame-shaped fixed portion placed on the machine base 11. The basic composition of the machine base 11 and the machine frame 12 are of frame compositions made of steel plates and some portions thereof are composed so as to be divisible.

A billet carrying equipment 2 is disposed on this machine base 11. This billet carrying equipment 2, comprising a movable chain conveyer 21 supported by a conveyer body 22, is disposed to extend linearly in left-right direction as shown in FIGS. 1 and 2. Billets 3, held on the trays 23 of this chain conveyer 21, move in the direction of the arrow E along with the movement of the conveyer 21. The trays 23 are attached to the chain conveyer 21. This chain conveyer 21 has sprocket wheels 25, 26 at both ends and the chain conveyer 21 circulates in an endless manner, being engaged with these sprocket wheel 25 (on the left side in FIGS. 1, 2) and sprocket wheel 26 (on the right side in FIGS. 1, 2). A driving equipment 27 for driving the conveyer is connected to one sprocket wheel 25 (see FIG. 2). Billets 3 are fed through a billet loading equipment 28 on the feeding side (on the right side in FIGS. 1 and 2) and discharged through a billet discharging equipment 29 on the discharging side (on the left side in FIGS. 1 and 2).

Billets 3 are fed from the feeding side (the right side in FIGS. 1 and 2) of the billet carrying equipment 2 and then have both end faces thereof subjected to determined working of grinding and, after then, discharged through the discharging side (the left side in FIGS. 1 and 2). On the upper side of this billet carrying equipment 2, a first grinding equipment for working on planar portions 4A, a first grinding equipment for chamfering 5A, a second grinding equipment for working on planar portions 4B and a second grinding equipment for chamfering 5B are provided, in the sequence from the feeding side of billets, on the machine base 11 along the billet carrying equipment 2. The first grinding equipment for working on planar portions 4A and the second grinding equipment for working on planar portions 4B are equipment for working on planar portions of end faces of billets 3. The first grinding equipment for chamfering 5A and the second grinding equipment for chamfering 5B are equipment for working of chamfering on circular edge portions of end faces of billets 3.

The grinding belts 46, 57 of the first grinding equipment for working on planar portions 4A and the first grinding equipment for chamfering 5A are disposed on the end face side on one side of billets 3 (on the upper side seen in FIG. 2) respectively. The grinding belts 46, 57 of the second grinding equipment for working on planar portions 4B and the second grinding equipment for chamfering 5B are disposed on the end face side on the other side of billets 3 (on the underside seen in FIG. 2) respectively. The first grinding equipment for working on planar portions 4A and the second grinding equipment for working on planar portions 4B are opposite hand, while these are of a same composition. Similarly, the first grinding equipment for chamfering 5A and the second grinding equipment for chamfering 5B are also opposite hand, while these are of a same composition. The main part of the present invention is composed of the above explained equipment. The detailed structure of each equipment will be explained below.

[Billet Carrying Equipment]

The billet carrying equipment 2 carries billets 3 with movement of the chain conveyer 21 that circulates in an endless manner. A driving equipment 27 is connected to the sprocket wheel 25 in the left end portion of the chain conveyer 21. Further, although not shown, the driving equipment 27 is provided with position detecting means (a rotation detector), which counts rotational frequency of the sprocket wheel 25 to detect the position of the carried tray 23. A rotary encoder, for example, is used as this position detecting means.

As shown in FIGS. 1, 5A, 5B, 6A, 6B and 6C, the conveyer body 22 is a frame body having side walls formed on its both sides in the direction of carrying billets 3, and the chain conveyer 21, disposed on the upper face of the conveyer body 22, circulates in the direction of carrying billets 3. As shown in FIG. 5A, 5B, 6A, 6B and 6C, trays 23, disposed at every other positions on the endless chain conveyer 21, circulates along the upper face of the conveyer body 22, move under the conveyer body 22 and then return to the initial position. Two guide rollers 24, 24 are provided on each side face in the lower portion of each tray 23. The trays 23 move in the direction of carrying billets 3 with the guide rollers 24, 24 guided by the conveyer body 22

Two rollers 231, 231 are provided on each side in the upper portion of each tray 23 and a billet 3 is placed over both of the two rollers 231, 231. Billets 3, placed on the rollers 231, 231 in a rotatable manner, are forcibly carried with the lengthwise position thereof restrained by the truing-up equipment 6 explained later.

[Truing-Up Equipment]

In the next, mechanism for arranging billets in course of carrying will be explained. As shown in FIGS. 1, 2, 6A, 6B and 6C, four truing-up equipment 6 are fixed on the side walls of the conveyer body 22. These truing-up equipment 6 are composed in opposite hand manner and each truing-up equipment is fixed on the side wall of the conveyer body 22. These truing-up equipments 6 guide billets 3 to be carried, truing up them to the optimum position for grinding. Four truing-up equipment 6, composed to be opposite hand respectively, are fixed to the side walls of the conveyer body 22, corresponding to the edge faces of billets 3 to be ground. FIG. 6A, FIG. 6B and FIG. 6C show a truing-up equipment 6 on one side in FIGS. 1 and 2 (at the right end in FIGS. 1 and 2), in which FIG. 6A is a front view of the truing-up equipment 6, FIG. 6B is a plan view of FIG. 6A and FIG. 6C are a cross-sectional view taken along the line B-B in FIG. 6A. The figure shows the situation of action of the truing-up equipment 6, in which a truing-up guide 62 is pushed via a pushing-out member 61 and a billet 3 on the tray 23 is trued up to the side of the first grinding equipment for working on planar portions 4A.

The pushing-out member 61 is provided in a movable manner in the direction across the conveyer body 22 (the left-right direction in FIG. 6C). The truing-up guide 62, having a guide portion 622 for carrying billets 3 formed thereon, make up an elongated member along the direction of carrying billets. When the truing-up guide 62 advances, the billet 3, being pushed by the guide portion 622 for carrying billets of the truing-up guide 62, is trued up to one side of the billet carrying equipment 2 (to the right side in FIG. 6C). When working on the planar portion and chamfering on the circular edge portion in one end face of a billet 3 have been accomplished by the first grinding equipment for working on planar portions 4A and the first grinding equipment for chamfering 5A respectively, the billet 3 comes to an intermediate position on the billet carrying equipment 2. Then, the billet 3 is pushed to the other side of the billet carrying equipment 2 (to the left side in FIG. 6C) by the third truing-up equipment 6. Working on the planar portion and chamfering on the circular edge portion in the other end face of the billet 3 are performed by the second grinding equipment for working on planar portions 4B and the second grinding equipment for chamfering 5B respectively. The truing-up guide 62 has a restraining portion of up-down movement 621 of billets 3 formed, which restrains and prevents the billet 3 from going up out of the rollers 231, 231.

The truing-up equipment 6 has adjustment handles 63, 64 attached thereto. The guiding width of the truing-up guide 62 is varied through adjustment of the pushing-out member 61 corresponding to the axial (longitudinal) length of the billet 3 with operation of the adjustment handle 63. Also, a lifting platform 65 is shifted up or down corresponding to the diametric dimension of the billet 3 with operation of the adjustment handle 64. The pushing-out member 61 is fixed to the lifting platform 65. The truing-up equipment 6 are provided at the position for grinding of each of the first grinding equipment for working on planar portions 4A, the first grinding equipment for chamfering 5A, the second grinding equipment for working on planar portions 4B and the second grinding equipment for chamfering 5B.

[First Grinding Equipment for Working on Planar Portions, Second Grinding Equipment for Working on Planar Portions]

The first grinding equipment for working on planar portions 4A and the second grinding equipment for working on planar portions 4B are to grind billets 3 at both end faces thereof. The first grinding equipment for working on planar portions 4A and the second grinding equipment for working on planar portions 4B are opposite hand, while they are of a same composition. So the explanation will be made as to the first grinding equipment for working on planar portions 4A and explanation of the second grinding equipment for working on planar portions 4B is omitted. As shown in FIGS. 1 to 4, the first grinding equipment for working on planar portions 4A is disposed on one end face side of billets 3 (upper side seen in in FIG. 2). Square pillars 41 is provided on the upper face of the machine base 11 and a first endless grinding belt equipment for working on planar portions 42 is provided on the square pillar 41. A large pulley 43 and a small pulley 44 are provided in a rotatable manner in the first endless grinding belt equipment for working on planar portions 42. The large pulley 43 is disposed on the feeding side of the billet carrying equipment 2 and connected to the output shaft of a driving motor 45 via transmission mechanism (not shown). The small pulley 44 is disposed on the discharging side of the billet carrying equipment 2 and has a structure such that the position thereof can be adjusted relative to the large pulley 43. The position adjustment means is one using screws, specific mechanism of which is well known in the art, so detailed explanation thereof is omitted here.

An endless, band-shaped grinding belt 46 is wound over the large pulley 43 and the small pulley 44 so as to circulate around them. Consequently, this grinding belt 46 circulates around the large pulley 43 and the small pulley 44, when driven by the driving motor 45. The circulation course of the grinding belt is arranged to be inclined in such a manner as to be higher in the discharging side than in the feeding side and the circulating direction F of the grinding belt 46 is opposite to the carrying direction of billets 3 (direction of the arrow E), as shown in FIG. 10A. That is, as shown in FIG. 10A, a plurality of billets 3 are carried so that they go across the width G of the grinding belt 46 successively in a direction inclined to the circulating direction F. Thus, arrangement is made such that the movement direction of the grinding belt 46 and the movement direction of billets 3 are crosses with an acute angle. In other words, billets 3 move in a diagonal direction of the rectangular face of grinding by the grinding belt 46. With this movement in a diagonal direction of billets, the whole face across the width the grinding belt 46 can be used evenly. While billets 3 pass through the grinding length H, working of grinding on the planar portion in one end face of each of the billets 3 is performed. Here, each billet 3 is rotated itself in the direction of the arrow J with resistance in grinding by the grinding belt 46 in the course of carrying from the feeding side to the discharging side.

In order to press the grinding belt 46 properly to the end face of a billet 3, a pressing equipment 47 is provided in the first endless grinding belt for working on planar portions 42. This pressing equipment 47 is one that presses the grinding belt 46 over the whole face of the grinding belt 46 along the lengthwise direction thereof in such a manner as to confront the end face of the carried billet 3. The pressing equipment 47 is composed of a plate-shaped member 471 directly pressed against the grinding belt 46 in such a manner as to confront the end face of the billet 3 and three adjusting bolts 472 for evenly pressing the plate-shaped member 471 against the end face of the billet 3. The first grinding equipment for working on planar portions 4A is composed in such a manner. Similarly, the second grinding equipment for working on planar portions 4B having a same composition is disposed on the side of the other end face of the billet 3 in such a manner as to be opposite hand.

[First Grinding Equipment for Chamfering, Second Grinding Equipment for Chamfering]

The first grinding equipment for chamfering 5A and the second grinding equipment for chamfering 5B are grinding equipment for chamfering the circular edge portions of billets 3 at both ends thereof. The first grinding equipment for chamfering 5A and the second grinding equipment for chamfering 5B are opposite hand, while they are of a same composition. So explanation will be made as to the first grinding equipment for chamfering 5A and explanation as to the second grinding equipment for chamfering 5B is omitted. As shown in FIGS. 1, 2 and 7 to 9, a grinding belt 57 of the first grinding equipment for chamfering 5A is disposed on one end face side of billets 3 (upper side as seen in FIG. 2). A pillar 51 is erected on the machine base 11 on the lower side as seen in FIG. 2. A supporting body 52 is provided on the pillar 51 so as to be movable upwards and downwards. A first endless grinding belt equipment for chamfering 53 is fixed to the supporting body 52.

This first endless grinding belt equipment 53 has a circulating, endless grinding belt 57. The grinding belt 57 is provided in the position where grinding for chamfering can be made so as to perform working on the circular edge portion on the end faces of billets 3. That is, the grinding belt 57 is placed so that the grinding face of the grinding belt 57 is inclined with an angle of about 45 degrees relative to the end face of a billet 3 and parallel to the direction of carrying billets 3. FIGS. 7 and 9 show the mechanism for moving the supporting body 52 upwards and downwards. As shown, two guide bushes 58, 58 are fixed to the front face 511 of the pillar 51 and the lower portion of each of guide bars 581, 581 is fitted into each of the guide bushes 58, 58 so as to slide upwards and downwards. A connecting plate 521 is fixed to the supporting body 52 on the back face thereof and the upper end of each of the guide bars 581, 581 is fixed to the connecting plate 521. Further, a hydraulic cylinder 582 is fixed to the pillar 51 on the front face thereof and the upper end of the piston rod 583 of the hydraulic cylinder 582 is fixed to the connecting plate 521. Consequently, the supporting body 52 is caused to move upwards and downwards relative to the pillar 51 by activating the hydraulic cylinder 582 with a solenoid valve (not shown).

FIG. 8A and FIG. 8B show the first endless grinding belt for chamfering 53, in which FIG. 8A is a front view of the first endless grinding belt equipment 53, FIG. 8B is a left side view of FIG. 8A. A large pulley 54 and a small pulley 55 are provided in a rotatable manner in the first endless grinding belt equipment for chamfering 53. The large pulley 54 is disposed on the side of the supporting body 52 and connected to the output shaft of a driving motor 56 via transmission mechanism (not shown). The small pulley 55 is disposed on the side apart from the supporting body 52 and has a structure such that the position thereof can be adjusted relative to the large pulley 54. The position adjustment means is one using screws, specific mechanism of which is well known in the art, so detailed explanation thereof is omitted here.

An endless, band-shaped grinding belt 57 is wound over the large pulley 54 and the small pulley 55 so as to circulate around them. Consequently, this grinding belt 57 circulates around the large pulley 54 and the small pulley 55, when driven by the driving motor 56. The grinding face of the grinding belt 57 is disposed so as to be inclined to the circular edge portion of a billet 3.

[Working Action of First Grinding Equipment for Working on Planar Portions 4A]

Billets 3 that have been cut with a cutting equipment (not shown) are fed to the billet carrying equipment 2 through the billet loading equipment 28 disposed in the right end of the grinding apparatus of billets at both end faces 1. With actuation of the truing-up equipment 6 disposed in the right end in FIG. 2, the truing-up guide 62 is pushed via the pushing-out member 61, which causes the billet 3 on the tray 23 to be trued-up to the side of the first grinding equipment for working on planar portions 4A. With actuation of the driving motor 45 of the first grinding equipment for working on planar portions 4A, working on the planar portion in one end face of the billet 3 is performed with the grinding belt 46, as shown in FIG. 10A.

[Working Action of First Grinding Equipment for Chamfering 5A]

The billet 3, of which working on the planar portion in one end face has been accomplished, is carried by the billet carrying equipment 2 to the position for working by the first grinding equipment for chamfering 5A. With actuation of the truing-up equipment 6 disposed next to one disposed in the right end in FIG. 2, the truing-up guide 62 is pushed via the pushing-out member 61, which causes the billet 3 on the tray 23 to be trued-up to the side of the first grinding equipment for chamfering 5A. The grinding belt 57 is disposed to be inclined to the billet 3, as explained above. FIG. 10B is an explanatory view in the case where the grinding belt 57 is disposed with about 45 degrees (from vertical direction as reference). The billet 3 is carried in the direction of the arrow E and the grinding belt 57 circulates in the direction of the arrow K. That is, the direction of movement of the grinding face of the grinding belt 57 and the direction of movement of the billet 3 cross with about 45 degrees in this example. The position where the billet 3 touches the grinding belt 57 is the upper end L of the circular edge portion of the billet 3. That is, the grinding belt 57 chamfers the billet 3 supported on a pair of rollers 231,231 so as to be rotatable as the billet 3 is rotated. Consequently, as the position of grinding of the billet 3 is in the upper end L of the circular edge portion of the billet 3, disposition of the grinding belt 57 is made so that the grinding face abuts on the upper end L of the circular edge portion of the billet 3.

With actuation of a hydraulic cylinder 582, the supporting body 52 is caused to move downwards relative to the pillar 51. The billet 3 touches the grinding face of the grinding belt 57 only within the intermediate area with a width M along the carrying direction E so that grinding is performed there. That is, when the upper end L of the carried billet 3 has come up to the position of the portion with a width N in the edge of the grinding belt 57, the position is detected by a position detecting means (not shown), so that the hydraulic cylinder 582 is actuated. The upper end L of the billet 3 is kept from touching the portions with a width N in the edges of the grinding belt 57. As the billet 3 is rotated, the upper end L of the circular edge portion in one end face thereof is ground within the above mentioned area with a width M. Thus, because the billet 3 is kept from touching the portions with a width N in the edges of the grinding belt 57, abrupt wear of the grinding belt at both edge portions thereof can be avoided and durability of the grinding belt 57 is improved.

In such a manner, the billets 3, for which working of grinding on the planar portions and chamfering on the circular edge portions in one end face thereof has been accomplished, are carried sequentially through the billet carrying equipment 2 to the second grinding equipment for working on planar portions 4B and the second grinding equipment for chamfering 5B. Working of grinding on the planar portions and chamfering on the circular edge portions in the other end face the billets 3 are performed and then working of grinding on both ends of the billets 3 is accomplished. After then, the billets are discharged through the billet discharging equipment 29 on the discharging side (left side in FIGS. 1 and 2). The grinding apparatus of billets at both end faces 1 according to the embodiment of the present invention is one that requires less energy for operation and less space for placement, because both of working on planar portions in end faces of billets and working of chamfering on circular edge portions are carried out with a single grinding apparatus.

While billets 3 are discharged after working of grinding on the planar portion and chamfering on the circular edge portion are performed once for each end face of billets 3, it is not necessary to limit the working and chamfering once for each end face of billets. That is, times for performing working of grinding on a planar portion and chamfering on a circular edge portion of a billet may be decided corresponding to the condition of the end face of a cut billet 3 (that is, performance of the cutting machine, or the like). Here, in the above explained case shown in FIG. 10A, the billet 3 is carried so as to cross the circulating direction F of the grinding belt 46 in an inclined direction. It is similar that the grinding belt 57 as shown in FIG. 10B is disposed with an angle of about 45 degrees. It is preferable to cause the billets to move in a diagonal direction on the rectangular grinding face, for utilize the grinding area of the grinding belt effectively and evenly.

While embodiment of the present invention has been explained above, the present invention is not limited to the embodiment. For example, while chamfering on circular edge potions is performed after working of grinding on planar portions has been accomplished in the embodiment, working of grinding on planar portions may be performed after chamfering on circular edge portions has been accomplished. Further, while, after working of grinding on planar portions and chamfering on circular edge portions in one end face of a billet 3 have been accomplished, working of grinding on planar portions and chamfering on circular edge portions in the other end face of the billet 3 is performed, it may be such that, after working of grinding on planar portions in one end face and the other end face of a billet 3 has been accomplished, chamfering on circular edge portions in one end face and the other end face of the billet 3 is performed.

EXPLANATION OF REFERENCE NUMBERS

1 grinding apparatus of billets at both ends

11 machine base

12 machine frame

2 billet carrying equipment

21 chain conveyer

22 conveyer body

23 tray

231 roller

24 guide roller

25 sprocket

26 sprocket

27 driving equipment

28 billet loathng equipment

29 billet discharging equipment

3 billet

4A first grinding equipment for working on planar portions

4B second grinding equipment for working on planar portions

41 pillar

42 first endless grinthng belt equipment for working on planar portions

43 large pulley

44 small pulley

45 driving motor

46 grinding belt

47 pressing equipment

471 plate-shaped member

472 adjusting bolt

5A first grinding equipment for chamfering

5B second grinding equipment for chamfering

51 pillar

511 front face

52 supporting body

521 connecting plate

53 first endless grinthng belt equipment for chamfering

54 large pulley

55 small pulley

56 driving motor

57 grinding belt

58 guide bush

581 guide bar

582 hydraulic cylinder

583 piston rod

6 truing-up equipment

61 pushing-out member

62 truing-up guide

621 restraining portion of up-down movement

622 guide portion for carrying

63, 64 adjustment handle

65 lifting platform 

1. A grinding apparatus of billets at both end faces comprising: a machine base, a billet carrying equipment that is provided on the machine base and carries a plurality of trays placing cut billets thereon from a feeding side to a discharging side, a first minding equipment for working on planar portions that is provided on the machine base and performs working on the planar potion in one end face of a billet with a first circulating endless grinding belt for working on planar portions, a second grinding equipment for working on planar portions that is provided on the machine base and performs working on the planar potion in the other end face of the billet with a second circulating endless grinding belt for working on planar portions, a first grinding equipment for chamfering that is provided on the machine base and performs working of chamfering on the circular edge portion in one end face of a billet with a first circulating endless grinding belt for chamfering, a first lifting equipment that is provided on the first minding equipment for chamfering and performs lifting movement of the first endless grinding belt so as to be attached to and detached from the billet, a second grinding equipment for chamfering that is provided on the machine base and performs working of chamfering on the circular edge portion in the other end face of the billet with a second circulating endless grinding belt for chamfering, and a second lifting equipment that is provided on the second grinding equipment for chamfering and performs lifting movement of the second endless grinding belt so as to be attached to and detached from the billet.
 2. The grinding apparatus of billets at both end faces according to claim 1, wherein: the first grinding equipment for chamfering is disposed adjacent to the first grinding equipment for working on planar portions towards the discharging side, the second grinding equipment for working on planar portions is disposed adjacent to the first grinding equipment for chamfering towards the discharging side, and the second grinding equipment for chamfering is disposed adjacent to the second grinding equipment for working on planar portions towards the discharging side.
 3. The minding apparatus of billets at both end aces according to claim 1, wherein: the billet carrying equipment carries horizontally a plurality of trays placing cut billets thereon from the feeding side to the discharging side, and the first endless grinding belt for working on planar portions and the second grinding belt for working on planar portions are composed so as to be inclined so that the discharging side is higher than the feeding side.
 4. The grinding apparatus of billets at both end faces according to claim 1, wherein: the movement direction of the billet carrying equipment crosses the movement direction of the grinding faces of the first endless grinding belt for working on planar portions and the second endless grinding belt for working on planar portions with an acute angle.
 5. The minding apparatus of billets at both end faces according to claim 1, wherein: the billet carrying equipment has a position detecting means that detects the carrying position of the tray for causing the first lifting equipment and the second lifting equipment to make up-down movement of the first endless grinding belt for chamfering and the second endless grinding belt for chamfering, to make a lifting movement respectively.
 6. The grinding apparatus of billets at both end faces according to claim 1, further comprising: a first truing-up equipment that is provided in the billet carrying' equipment and carries the billets on the trays such that the billets are trued-up on one side of the carrying course of the billet carrying equipment, and a second truing-up equipment that is provided in the billet carrying equipment and carries the billets on, the trays such that the billets are trued-up on the other side of the carrying course of the billet carrying equipment. 